Belt tensioning apparatus

Abstract

The disclosure relates to a tensioning system for a drive belt (17). The system includes a tensioner (19) which is mounted to slide towards, and away from, the belt. An idler roller (22) is resiliently mounted in the tensioner (19) and is forced against the belt by means of springs, for example (84 and 85) in FIG. 8 or (102 and 103) in FIG. 9. The springs are arranged so that they increase the force applied by the roller to the belt as the tensioner is moved towards the belt until the force reaches a predetermined value, whereafter further movement over a limited range does ot further increase the force. The invension provides a tensioning system which will provide a predetermined lateral pressure on the belt without the necessity for using measuring apparatus during the adjustment of the static belt tension.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is as follows: 
     
       1. A tensioning system for a drive belt passing around at least two pulleys, comprising in combination; a tensioning member which is mounted in a housing which is movable toward and away from said drive belt in order to deflect said drive belt;   said tensioning member being urged towards said drive belt by a spring action between said tensioning member and said housing, said spring requiring an increasing force to increase its deflection up to a predetermined limit, but which, when this limit is reached, can be deflected over a predetermined range without any further increase in the applied force;   said spring adapted to increase the force applied by the member to the belt as it is moved towards the belt until the force reaches said predetermined limit, whereafter further movement over said predetermining range does not further increase said force.   
     
     
       2. A tensioning system according to claim 1, wherein said tensioning member is an idler roller fixed to an axle which is rotatable in a pair of guide plates slidable in a housing. 
     
     
       3. A tensioning system according to claim 2, wherein each of said guide plates is provided with a spigot on which is mounted a helical spring having two generally radially extending end portions which bear on said housing. 
     
     
       4. A tensioning system according to claim 1, wherein the tensioning member is an idler roller rotatably mounted on an axle which is secured to a pair of springs accommodated in a housing. 
     
     
       5. A tensioning system according to claim 4, wherein each of said springs comprises a generally flat central portion secured to said axle, two end portions contained in a plane substantially parallel to, but displaced from, the plane of said central portion, and two intermediate portions connecting said central portion to said two end portions and capable of collapsing when a predetermined force is applied between said central portion and said two end portions. 
     
     
       6. A tensioning system according to claim 1, wherein said spring means comprises a strip of resilient material folded to provide a central peak between two valleys and two end portions extending outwardly from said valleys away from said peak. 
     
     
       7. A tensioning system according to claim 6, wherein the end portions of said strip are supported in said housing and force is applied to an axle on which a drive roller is rotatable by said peak. 
     
     
       8. A tensioning system according to claim 1, wherein said spring means is designed to provide an audible sound when the force reaches said predetermined value. 
     
     
       9. A tensioning system according to claim 1, wherein said spring comprises two angular portions interconnected by a resilient frustoconical portion which collapses when a predetermined force is applied, urging one of said angular portions towards the other. 
     
     
       10. A tensioning system according to claim 1, wherein said spring comprises a helical spring having two end portions extending substantially radially, one from each end of the helical portion. 
     
     
       11. A tensioning system according to claim 10, wherein the end portions of said spring are supported in said housing and wherein a force is applied to an axle on which an idler roller is rotatable by the helical portion of said spring. 
     
     
       12. A tensioning system according to claim 1, wherein the spring means, is a laterally unsupported helical compression spring adapted to buckle when the applied force reaches a predetermined limit. 
     
     
       13. A tensioning system according to claim 12, wherein one end of said compression spring bears on said housing and the other end of said compression spring bears on an axle rotatably supporting said idler roller.